1. Field of the Invention
This invention relates to a continuous oven for making baked ware, comprising an elongate oven space provided with upper and lower radiant heaters, which are connected to be flown through in operation by heating gases, a revolving endless baking belt having a baking belt course for transporting the material to be baked through the oven space, and a heat exchanger for heating the air for the oven space, wherein the radiant heaters are connected to at least one heating gas circulating circuit, which is provided with an exhaust gas outlet, a fresh air inlet, and at least one heating gas generator.
2. Description of the Prior Art
In a traveling-hearth baking oven disclosed in Published German Application 1,532,904 the oven space is heated by heating gases, which are generated in a combustion chamber and are passed through the heating gas ducts, which are disposed above and below the oven space and consist of radiant heaters, and the gases are subsequently discharged as exhaust gases. The air for the oven space is sucked off and is replaced by preheated fresh air, which is initially preheated by the returning baking belt or in a heat exchanger, which is flown through by the air which has been sucked from the oven space, and the fresh air is subsequently passed through a recuperator, which is heated by the exhaust gases from the oven. Thereafter the fresh air is intermittently injected into the oven space. The fresh air may be heated up further in the combustion chamber in which the heating gases for the oven are generated. There is no circuit for circulating the heating gases.
EP 0 334 001 A1 discloses a continuous oven for making baked ware, which comprises two separate and separately controllable heating gas circuits for the upper heat and the lower heat, respectively. In that oven the burners for generating the respective heating gases are spaced apart along the oven space in the associated heating gas duct, which is disposed directly above and below the oven space, respectively. That continuous oven is provided with two water vapor exhaust ducts, which extend through the upper heating gas duct, and with water vapor-circulating means, which are disposed in the last one-third of the oven and serve to circulate water vapors transversely to the direction of travel of the baking belt. A supply of preheated air for the oven space has not been contemplated.
Swiss Patent Specification 356,100 discloses a travelling-hearth breadbaking oven that comprises an indirectly heated oven space and variable means for circulating air through the oven space along the latter. The oven space is heated by upper and lower heating gas ducts, which are flown through by heating gases. The air for the oven space is circulated along length sections of the oven space, which length sections differ in length by means of two fans and a duct system, which opens into the oven space through shut-off valves, which are distributed over the length of the oven space. A single circuit for circulating air for the oven space or two separate ones of such circuits, which are connected in series may be provided. The duct system comprises two ducts for supplying fresh air, which may be preheated. A supply of air which has been preheated by a heat exchanger to the oven space has not been contemplated.